The invention relates generally to apparatus for cutting continuous strands of material and more particularly for cutting continuous strands of material such as fiberglass and particularly wet fiberglass into short lengths, i.e., staple fibers or wet chop, in a continuous process.
As a reinforcing constituent of numerous materials, fiberglass has found broad application. Generally speaking, the matrix that short glass fibers forms when suspended in various plastics and organic materials is responsible for their toughness and ruggedness. In this application, it is desirable for the glass fibers to take the form of uniform short fibers or staples. The production of such staple fibers from continuously produced glass has been the object of much research and development.
For example, U.S. Pat. Nos. 3,485,120 and 3,557,648 disclose methods and apparatus for cutting elongated material of the type generally referred to as outside-in choppers. Here, a wheel with radially oriented blades disposed about its periphery receives the elongated material. Disposed adjacent the bladed wheel is an idler which forces the strands into the blades as the material builds up upon the bladed wheel. The cut fibers move radially inwardly and are harvested from the center of the wheel.
U.S. Pat. No. 3,861,257 teaches an inside out chopper that is, a chopper having blades in an outer position and idler and supply means in an inner position. In this device, the blades are fixed. A plurality of pressure rollers are rotatably supported on a central wheel and revolve about the center axis. The rollers are spring loaded. The elongate material is provided into the region between the outer faces of the rollers and the faces of the knife blades and the force of the rollers and increasing thickness of the material cuts the strands into short fibers which move radially outwardly through the blades.
U.S. Pat. No. 3,948,127 also teaches an inside out chopper. In this apparatus, knife blades are disposed in a ring or outer wheel which rotates about a center axis. Multiple pinch rollers though rotatable about their own axis are fixed in position. An endless belt traverses the rollers as well as a grouping of interior rollers one of which is spring loaded to maintain tension on the belt. The endless material such as tow is provided into the center of the machine and ooze out onto the endless belt. As the material builds up, it is forced into the knife blades and cut. Harvesting of the staple fibers is accomplished about the periphery of the knife ring. U. S. Pat. No. 3,978,751 discloses a similar chopper wherein a ring of knife blades are disposed in a ring and a belt circulates about the interior of the ring on a pair of symmetrical eccentric cams. The knife blades rotate and where the clearance between the cam supported belt and blades is the smallest, the fibers are cut.
Also of interest is the device disclosed in U. S. Pat. No. 4,369,681. Here a ring of inwardly facing knife blades is rotated while an idler having a diameter at least one half the inside diameter defined by the inner faces of the blades forces the fibers against the knife blade where they cut. The fibers are collected about the periphery of the knife ring. The pressure roller is not driven and includes mounting means which facilitate moving the roller from a working to a non-working position.
From the foregoing review of the prior art, it will be appreciated that improvements relating to the construction and operation of apparatus for chopping continuous strands of elongate material into short, staple fibers are not only desirable but possible.